In the context of the neurobiology of trauma, how does dysregulation of the HPA axis manifest physically or psychologically?

Dysregulation of the HPA (hypothalamic-pituitary-adrenal) axis, the body's primary stress response system, following trauma manifests in a variety of physical and psychological symptoms. Physically, dysregulation can lead to chronic fatigue, sleep disturbances (insomnia or hypersomnia), gastrointestinal problems (irritable bowel syndrome, stomach aches), weakened immune system (increased susceptibility to illness), and chronic pain. This occurs because the HPA axis normally regulates the release of cortisol, a stress hormone. In chronically stressed individuals, the HPA axis can become either overactive, leading to excessive cortisol release, or underactive, leading to insufficient cortisol release. Psychologically, HPA axis dysregulation can contribute to anxiety disorders (panic attacks, generalized anxiety), depression, difficulty concentrating, memory problems, irritability, emotional lability (rapid mood swings), and an increased risk of developing PTSD. For example, some trauma survivors have an exaggerated startle response due to a persistently heightened state of physiological arousal caused by HPA axis dysregulation. Others may experience emotional numbing and detachment, reflecting an underactive HPA axis and reduced cortisol levels. The specific symptoms depend on the individual's unique biological makeup, the nature of the trauma, and other factors.